It is an object of the present invention to provide a papermaking felt which is not only effective to dewater a wet paper web and to smooth the surface thereof but also shows an improved anti-dehairing property of a staple fiber web, and more specifically a papermaking felt which is capable of improving surface smoothness of a wet paper web and usable especially in a high-speed papermaking machine.
A papermaking process with a papermaking machine consists of three main parts, namely, forming, press, and drying sections, through which a wet paper web is dewatered successively. Papermaking equipments with a dewatering function are employed in each section, which is a papermaking felt in the press section.
Conventionally, a papermaking felt has had functions to dewater a wet paper web (dewatering capability), improve smoothness of a wet paper web (smoothness), and transfer a wet paper web (a capability to transfer a wet paper web). A papermaking felt is required to have a balanced combination of these basic functions.
Water within a wet paper web is either discharged from the underside of the felt after moving into the felt due to pressure as the wet paper web passes between a pair of press rolls, or discharged outside of the felt after vacuumed up in a suction box of a papermaking machine. Accordingly, important functions required for the felt are water permeability and a capability for a compressed felt to rebound without flattening when depressurized. It is also important for such functions to endure use.
Mainstream types of a typical papermaking felt are batt-on-base or batt-on-mesh types in which a staple fiber web is implanted into a woven fabric by means of needle punching. Recently, the batt-on-mesh type is favorably used in a high-speed papermaking machine, which leads to an increasing attention to surface smoothness of a wet paper web and anti-dehairing property of a staple fiber web.
Referring to FIG. 1, a structure of a typical felt is to be described. A papermaking felt 10 is an endless belt, and comprises a base body 20 made of a woven fabric or others and a staple fiber web (staple fiber) layer 30 which is intertwiningly integrated with the base body 20 by needle punching. The base body 20 is to provide the felt 10 with mechanical strength, which is a woven fabric made of a machine direction (MD) yarn 50 and a cross machine direction (CMD) yarn 40 in FIG. 1.
As already mentioned, the felt 10 is used in a press section of a papermaking machine (not shown in the figure), tensioned by guide rolls. It dewaters a wet paper web, as subjected to high pressure together with the paper web in the press section composed of a pair of press rolls or a press roll and a shoe. The felt 10 drives with the rotation of the press rolls.